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Taeyoung Kim,Eonjoo Park,Jun Suk Eun,Eun-young Lee,Ji Won Mun,Yunsang Choi,Shinyoung Lee,Hansol Yeom,Eunkyoung Kim,Jongmu Kim,Jihyun Choi,Jinho Ha,Sookkyung Park 한국역학회 2023 Epidemiology and Health Vol.45 No.-
OBJECTIVES: As few mpox cases have been reported in Korea, we aimed to identify the characteristics of mpox infection by describing our epidemiologic investigation of a woman patient (index patient, the third case in Korea) and a physician who was infected by a needlestick injury (the fourth case). METHODS: We conducted contact tracing and exposure risk evaluation through interviews with these 2 patients and their physicians and contacts, as well as field investigations at each facility visited by the patients during their symptomatic periods. We then classified contacts into 3 levels according to their exposure risk and managed them to minimize further transmission by recommending quarantine and vaccination for post-exposure prophylaxis and monitoring their symptoms. RESULTS: The index patient had sexual contact with a man foreigner during a trip to Dubai, which was considered the probable route of transmission. In total, 27 healthcare-associated contacts across 7 healthcare facilities and 9 community contacts were identified. These contacts were classified into high (7 contacts), medium (9 contacts), and low (20 contacts) exposure risk groups. One high-risk contact was identified as a secondary patient: a physician who was injured while collecting specimens from the index patient. CONCLUSIONS: The index patient visited several medical facilities due to progressive symptoms prior to isolation. Although the 2022 mpox epidemic mainly affected young men, especially men who have sex with men, physicians should also consider mpox transmission in the general population for the timely detection of mpox-infected patients.
Sound visualization of smartphone-radiated noise using nearfield acoustic holography
Taeyoung Park,Seonghun Im,Dong-Hyun Kim,Sangbeom Woo,Inman Jang,Won-Suk Ohm,Heungkil Park,Sehun Park,Guwon Ji 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
A smartphone contains electronic components that can inadvertently act as sources of unwanted vibration and noise. Also known as the "buzz," the noise is produced primarily by multilayer ceramic capacitors, the piezoelectric pulsation of which drives the circuit board into vibration, hence sound radiation. Given the close proximity of the smartphone to the ear, the audible noise, albeit low in amplitude, can be a nuisance and degrade the call quality. Thus accurate measurement and analysis of the noise are needed as the first step toward resolving the problem. The popular farfield-based techniques, however, are not applicable to smartphone-radiated noise because of its low sound pressure level (~20 dB). This paper presents an alternative method based on nearfield acoustic holography (NAH), here tailored for a small mobile device radiating low-intensity noise. The NAH method is shown to be capable of visualizing sound pressure and intensity anywhere near the smartphone as well as the vibration of the circuit board, which could lead to an effective design strategy for a quieter smartphone.
전산유동 해석을 이용한 30㎿<SUB>th</SUB> Oxy-PC 버너 설계 및 운전조건 평가
채태영(Taeyoung Chae),류창국(Changkook Ryu),양원(Won Yang) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.43
This study is aimed to conceptually design an oxy- pulverized coal (PC) burner which can be operated in both air and oxygen condition, using computational fluid dynamics (CFD). In this study, CFD analysis was performed to understand the combustion characteristics inside a tangential vane swirl type 30㎿ coal burner for air-mode and oxy-mode operations. In oxy-mode operations, various compositions of primary and secondary oxidizers were assessed which depended on the recirculation ratio of flue gas. In the simulation results for oxy-model operation, the reduced swirl strength of secondary oxidizer increased the flame length due to lower specific volume of CO₂ than N₂. The flame length was also sensitive to the flow rate of primary oxidizer. Further numerical investigations are required to improve the burner design combined with more detailed experimental results.
전산유동해석을 이용한 100 MW<SUB>e</SUB>급 석탄 순산소 연소 실증 보일러의 설계 및 운전조건 평가
채태영(Taeyoung Chae),박상현(Sanghyun Park),홍재현(Jaehyeon Hong),양원(Won Yang),이상훈(Sanghoon Lee),류창국(Changkook Ryu) 한국연소학회 2011 한국연소학회지 Vol.16 No.2
??As one of the main technologies for carbon capture and storage in power generation, oxy-coal combustion is being developed for field demonstration in Korea. This study presents the results of numerical simulation for combustion in a single-wall-fired 100 MWe-scale boiler proposed for the initial design of the demonstration plant. Using a commercial CFD code, the detailed combustion, flow and heat transfer characteristics were assessed both for air-mode and oxy-mode combustion. The results show that stable combustion can be achieved in the dual mode operation with the current boiler configuration. However, the differences in the flow pattern and heat transfer between the two combustion modes need to be considered in the design and operation which is mainly due to the larger density and specific heat of CO₂ compared to N₂. Further development of the boiler design is required using improved numerical modeling for radiative heat transfer and combustion.
80 kW<SUB>th</SUB>급 미분탄 연소 시스템에서 하수슬러지 혼소시 연소 특성 연구
채태영(Taeyoung Chae),이재욱(Jaewook Lee),이영재(Youngjae Lee),양원(Won Yang) 한국청정기술학회 2019 청정기술 Vol.25 No.1
하수슬러지의 열화학적 처리는 수분을 제거하여 연료로 사용되는 하수슬러지의 수분 함량을 낮추어 주는 기술이다. 열화학적 처리된 하수슬러지는 열량이 높아지기 때문에 에너지 집약적 과정이라고 할 수 있다. 이러한 공정 중에 소비되는 에너지를 절약하기 위해 하수슬러지의 수열 탄화 공정을 사용하였다. 수열탄화 공정은 하수슬러지를 사전 건조 없이 깨끗한 고체연료로 전환할 수 있다. 본 연구는 수열탄화 하수슬러지와 미분탄 연소 시스템의 혼소 특성을 조사하는 것을 목적으로 한다. 혼소 시 생성되는 유해물질 및 연소 효율의 변화를 측정하는 것을 목적으로 한다. 본 연구에 사용 된 연소 시스템은 80kWth급 연소로로서 1기의 선회류 버너가 장착되어 있다. 두 가지의 석탄을 주 연료로 사용하였고, 하수슬러지의 혼소율은 열량 기준 0% ~ 10%까지 진행하였다. 실험 결과 NOx는 400 ~ 600 ppm, SOx는 600 ~ 700 ppm 사이를 유지하였고, CO는 100 ppm 전후로 일정하게 유지되어 안정적인 연소를 확인할 수 있었다. 하수슬러지를 혼소할 경우, 혼소율이 증가할수록 NOx와 SOx의 배출량도 증가하였으나 그 편차가 크지 않았다. 연소 배가스에 포함된 오염 물질 배출은 혼소 비율 보다 주 연료인 석탄의 조성에 의해 크게 영향을 받는 것으로 밝혀졌다. Thermochemical treatment of sewage sludge is an energy-intensive process due to its high moisture content. To save the energy consumed during the process, the hydrothermal carbonization process for sewage sludge can be used to convert sewage sludge into clean solid fuel without pre-drying. This study is aimed to investigate co-firing characteristics of the hydrothermally carbonated sewage sludge (HCS) to a pulverized coal combustion system. The purpose of the measurement is to measure the pollutants produced during co-firing and combustion efficiency. The combustion system used in this study is a furnace with a down-firing swirl burner of a 80 kWth thermal input. Two sub-bituminous coals were used as a main fuel, and co-firing ratio of the sewage sludge was varied from 0% to 10% in a thermal basis. Experimental results show that NOx is 400 ~ 600 ppm, SOx is 600 ~ 700 ppm, and CO is less than 100 ppm. Experimental results show that stable combustion was achieved for high co-firing ratio of the HCS. Emission of NOx and SOx was decreased for higher co-firing ratio in spite of the higher nitrogen contents in the HCS. In addition, it was found that the pollutant emission is affected significantly by composition of the main fuel, regardless of the co-firing ratios.
죽탄 및 죽초액 제조를 위한 인도네시아산 및 국내산 대나무의 탄화특성 비교 연구
양원(Won Yang),김희열(Hui Yeol Kim),채태영(Taeyoung Chae),K. Ibik,H.G. Pohan 한국연소학회 2010 한국연소학회지 Vol.15 No.1
Carbonization characteristics of Indonesian bamboos were investigated using lab-scale tube furnace, in order to find optimum design temperature of a carbonizer for producing bamboo charcoal and vinegar. The bamboo samples used in this study are local bamboos from Damyang in Korea, Andong and Petung in Indonesia. Correlation of electric resistance, specific surface area and pH of bamboo vinegar with pyrolysis temperature has been investigated. Electric resistance of the charcoal increased for higher pyrolysis temperature the specific surface area was also increased as carbonization temperature got higher. Charcoal which has specific surface area of over 300 ㎡/g could be produced at 700℃. pH of bamboo vinegar was decreased for highter carbonization temperature and vinegar under pH 3 could be produced for all bamboo samples. In this experimental condition, it was found that lower carbonization temperature is better for producing bamboo vinegar of high quality, while higher temperature is better for obtaining bamboo charcoal with larger surface.
Edge Charge Singularity of Conductors
황치옥,Taeyoung WON 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
In this paper, we investigate a diusion-based simulation method for the edge singularity of a conducting object, rapidly evaluating the power-law singularity associated with the edge of the conducting object for the computation of capacitance coecients for VLSI interconnection systems. We show that for the edge singularity of a conducting object the edge distribution in the last-passage method can be approximated to be proportional to the potential dierence at a point very near to the conducting object from the potential of the conducting object. One exemplary application of this method to the cube edge is in good agreement with the previous result.